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Pathology > PNS/Muscle 2 > Flashcards

PNS/Muscle 2 Flashcards

1
Q

PACKET I

A
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2
Q

What are the two main nerve responses to injury?

A
  • Segmental demyelination
    • Schwann cell dysfunction or sheath damage
    • denuded axon indues remyelination by stimulating Schwann stemm cell proliferation
  • Axonal degeneration
    • primary destruction of the axon with the myelin sheath being secondary
    • Wallerian degeneration
    • Schwann cell catabolizes myelin and then macrophages “clean up”
    • chromolysis (loss of nissl bodies) and perikaryon swelling
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3
Q

With attempt at remyelination what occurs with the schwann cells? Myelin? Axon?

A
  • Schwann cells
    • proliferate and with multiple attempts to remyelinate they form an “onion bulb”
  • Myelin
    • thinner than previously
  • Axon
    • shorter internodal spaces
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4
Q

What is the growth cone of the axon?

A

Multiple filopodia and lamellapodia that lead small, closely aggregated, thinnly myelinated axons along the cord of schwann cells. Very slow growth (1mm/day)

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5
Q

Electrophysiology of axonal neuropathy?

Electrophysiology of demyelinating neuropathy?

A
  • Axonal
    • reduced signal strength due to axon dropout
  • Demyelinating
    • reduction in conduction velocity due to decreased myelin
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6
Q

Guillan Barre Syndrome:

Cause? What occurs to the nerve?

A
  • 2/3 are preceeded by influenza like illness
    • Campylobacter jejuni
    • Prior vaccinations
  • However, it is due to immune response
  • Inflammation and demyelination of roots and nerves
    • perivenular and endoneural infiltration of lymphocytes, macrophages, and few plasma cells
    • Macrophages penetrate at nodes and peel away myelin layers
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7
Q

Guillain Barre:

Clinical?

Cause of death?

A
  • Clinical concern is motor with ascending paralysis
    • Elevation in CSF protein
    • Altered vaso-permeability, especially in spinal roots
  • Prominent segmental demyelination
  • COD: due to respiratory paralysis, autonomic instability, cardiac arrest, or complication of treatment
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8
Q

What is Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)?

A
  • Chronic or subacute radiculoneuropathy
    • no preceeding infection
  • Often symmetric
  • Mixed sensorimotor polyneuropathy
  • Well developed “onion bulbing” due to ongoing injury
  • Remissions may occur with steroids of plasmapharesis
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9
Q

Neuropathy associated with systemic autoimmune disease:

Type of neuropathy?

Diseases associated?

A
  • Polyneuropathy
    • Distal sensory or sensorimotor
  • RA
  • SLE
  • Sjogren
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10
Q

What does neuropathy associated with vasculitis present as? What occurs?

A
  • Mononeuritis multiplex
    • mononeuritis or polyneuropathy possible
  • Patchy axonal degeneration and loss
  • Perivascular inflammatory infiltrates
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11
Q

Leprosy:

How is morphology determined?

What are the two types?

A
  • Morphology determined by cellular immune response
  • Types
    • Lepromatous
    • Tuberculoid
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12
Q

What occurs in lepromatous leprosy?

A
  • Schwann cell invaded by bacteria
    • segmental demyelination and remyelination
    • Loss of both myelinated and unmyelinated fibers
  • Endoneurial fibrosis
  • Thickening of perineural sheaths

Overall: symmetric polyneuropathy with primary sensory loss in cooler extremities

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13
Q

How does tuberculoid leprosy present?

A
  • Active cell mediated response
    • nodular granulomatous inflammation in dermis
    • injury to cutaneous nerves
    • perineural and endoneural fibrosis
  • T cell response
  • More localized nerve damage of axons, schwann cells, perineural and endoneural layers
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14
Q

Lyme disease presentation?

A
  • Due to dorrelia burgdorferi (spirochete)
  • Variable presentation
    • asceptic meningitis
    • mild encephalopathy
    • Polyradiculoneuropathies
    • Facial nerve palsies
      • either unilateral or bilateral
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15
Q

In HIV what occurs in the early stage versus what occurs in the late stage?

A
  • Early stage
    • mononeuritis multiplex and demyelinating disorders
    • similar to acute or chronic demyelinating diseases
  • Late stage
    • distal sensory neuropathy, often painful
    • Loss of myelin integrity
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16
Q

Diptheria:

What is it caused by/what does it look like?

Main cause of damage? Result?

A
  • Corynebacterium diphtheriae
    • G+ rod with clubbed ends
  • Exotoxin
    • initially causes paresthesia/weakness
    • early loss of proprioception/vibratory sense
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17
Q

Diphtheria:

How does the toxin get to the NS?

A
  • Enters sensory ganglia due to incomplete blood nerve barrier
  • Demyelination extends into adjacent anterior and posterior roots
  • Mixed sensorimotor nerves
  • The toxin blocks protein synthesis
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18
Q

What is VZV?

A
  • Latent infection of sensory ganglia of the SC and brainstem
  • Reactivation causes painful vesicular skin eruptions along a dermatome
    • thoracic and trigeminal nerves are most common
  • Ganglia show neuronal destruction and loss
  • Nerves show axonal degeneration after death of a sensory neuron
  • May have persistant postherpetic neuralgia syndrome
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19
Q

4 types of acquired metabolic and toxic neuropathies?

A
  1. Diabetes
  2. Metabolic, hormonal, and nutritional
  3. Toxic
  4. Tumor associated syndromes
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20
Q

Diabetic neuropathy:

Mechanism?

2 most common neuropathies?

A
  • Mechanism: non-enzymatic glycation of proteins and a change in function
    • mass reaction due to abundance of glucose
  • Ascending Distal symmetric sensorymotor neuropathy (most common)
    • primarily axonal of small fibers
    • endoneurial arterioles show vascular thickening
  • Autonomic neuropathy (20-40%)
    • Nearly always with distal symmetric sensory or sensorimotor neuropathy
    • Postural htn, incomplete emptying of bladder (increased infections), sexual dysfunction
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21
Q

PNS/MUSCLE II

A
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22
Q

What occurs in uremic neuropathy?

A
  • Axonal damage with secondary demyelination
  • Distal symmetric neuropathy
    • fine motor
  • Some recover with dialysis
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23
Q

What neuropathies are associated with thyroid dysfunction?

A
  • Hypothyroidism
    • carpal tunnel syndrome
    • distal symmetric sensory polyneuropathy
  • Hyperthyroidism
    • GB type syndrome
    • demyelination
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24
Q

Alcohol’s effect on nerves?

A
  • Primarily axonal
  • Directly toxic to nerves
  • Independent from possible related thiamine deficiency
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25
Q

In regards to nerves what could a pancoast tumor cause? Pelvic tumor?

A
  • Pancoast
    • brachial plexopathy
  • Pelvic
    • obturator palsy
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26
Q

In regards to compression what can tumors in the head cause? What about the cauda equina involvment in minengral carcinomatosis?

A
  • Tumors in head
    • cranial nerve palsy
      • Bell’s palsy
  • Cauda equina
    • polyradiculopathy of lower limb
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27
Q

Paraneoplastic neuropathy is typically associated with what cancer? What are the two types of lesions?

A
  • Small cell lung carcinoma
  • Slowly progressive sensorimotor lesion
    • most common
    • diffuse and symmetric
  • Pure sensory with degeneration of DRG neurons
    • less common
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28
Q

Neuropathy associated to IgM paraprotein? Mechanism?

A
  • Binding of antibody to myelin associated glycoprotein
  • Demyelinating neuropathy
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29
Q

Neuropathys associated with IgG or IgA?

Syndrome associated?

A
  • Demyelinating neuropathy
    • deposition in uncompacted myelin
  • POEMS syndrome
    • Polyneuropathy
    • Organomegaly
    • Endocrinopathy
    • Monoclonal gammopathy
    • Skin change
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30
Q

Role of light chain amyloid in neuropathy?

A
  • Vascular insufficiency or direct toxicity to axons
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31
Q

4 types of hereditary neuropathies?

A
  • Hereditary motor and sensory neuropathy (HMSN)
    • mutations in genes for formation/maintenance of myelin
  • Hereditary sensory neuropathy w/ or w/o autonomic neuropathy
    • limited to numbness, pain, and autonomic dysfunction
  • Familial amyloid polyneuropathy
    • amyloid deposition due to mutation in transthyretin gene (AD)
  • Peripheral neuropathy accompanying inherited metabolic disorder
    • ALD (x-linked), porphyria (AD)… etc
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32
Q

Charcot-Marie Tooth 1:

Inheritance?

When does it present?

What occurs to the nerves and body?

A
  • AD in childhood or early adulthood
  • Repeated segmental demyelination (onion)
  • Hypertrophy of individual peripheral nerves
    • may be palpable
  • Distal leg weakness
  • Progressive muscular atrophy of the calf (peroneal muscular calf atrophy)
  • Pes cavus: characteristic look of calf and foot
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33
Q

Charcot-Marie Tooth 1:

CMT1A genetics versus CMT1B?

A
  • CMT1A
    • duplication of C17 (segmental trisomy)
    • Encodes for peripheral myelin protein 22
    • Transmembrane protein involved in compact myelin
  • CMT1B
    • mutation on C1
    • Gene for myelin protein zero (MPZ)
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34
Q

CMT2:

What is the form?

Inheritance?

What happens to the nerves?

A
  • Neuronal form: affects the axon (no onion)
  • AD
  • NO nerve enlargement
  • Loss of myelinated axons
  • No segmental demyelination
    • normal conduction velocity
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35
Q

Most common subtype of Charcot Marie Tooth 2? Genetics involved?

A
  • CMT2A
    • Mutations in MFN gene involved in normal mitochondrial fusion
    • Presents in early childhood
36
Q

X linked Charcot marie tooth genetic mutation?

A

Mutation in GJB1 gene that codes for connexin 32

37
Q

Hereditary neuropathy with pressure palsy:

What is the mutation?

Type of neuropathy?

A
  • Deletion of the gene for PMP22
  • Transient motor and sensory neuropathy triggered at sites prone to entrapment
    • resolves in weeks to months
    • may progress to chronic neuropathy
  • Swollen, bulbous myelin sheath near nodes
38
Q

What happens to the nerve with a laceration or avulsion?

A
  • Axon degenerates distally
  • Regeneration depends on the continuity of the nerve
    • If cell body is preserved it will attempt to regenerate
  • Neuroma may develop
    • Disorganized axons with CT
39
Q

Types of compression neuropathies?

A
  • Carpal tunnel syndrome
    • median nerve numbness/parasthesia
    • frequently bilateral
    • frequently due to repetitive motion
  • Ulnar
  • Radial - saturday night palsy
  • Mortons neuroma
    • intermetatarsal sites
    • in women who wear heals
40
Q

Disease of the neuromuscular junction?

A
  • Myasthenia gravis
  • Eaton-Lambert myasthenic syndrome
  • Congenital myasthenic syndromes
  • Disorders caused by toxins
41
Q

Myasthenia gravis:

2 causes?

Diagnosis?

A
  • Autoantibodies to acetylcholine receptors on postsynaptic membrane (85%)
  • Antibodies against muscle specific receptor tyrosine kinase
    • interference with trafficking/clustering
    • no compliment involved
  • Both result in decreased ACh receptor function
  • Tensilon test: anticholinesterase given to help diagnose
42
Q

Myasthenia gravis:

Who is targeted?

Muscle response?

Symptoms?

A
  • Younger women and older men
  • Decreased muscle response with repeated stimulation
  • Symptoms/signs
    • General weakness
    • Extraocular muscles usually involved with drooping ptosis and diplopia
43
Q

Eaton-Lambert:

Causes?

Presentation?

A
  • Due to paraneoplastic syndrome with antibodies against pre-synaptic voltage gated Ca++ channels (lung cancer)
  • Patients without a tumor often have other autoimmune features/diseases
  • Presentation
    • weakness in extremities
    • INCREASED muscle response with repeated stimulation
44
Q

Congenital myasthenic syndromes:

Inheritance pattern?

Type of mutations?

When do they present?

A
  • AR
  • Loss of function in genes of presynaptic, synaptic, or postsynaptic proteins
  • Severe forms present in infancy
  • Milder forms present later
45
Q

Toxin that affects the neuromuscular junction? Mechanism of action? REsult?

A
  • Botox (clostridum botulinum)
    • Prevents ACh release at presynaptic membrane
    • Flaccid paralysis
46
Q

What is collateral reinnervation? What occurs to muscle cell types?

A
  • When there is axonal degeneration and healthy axons then take over and innervate the muscle
  • The muscle cell type changes to match the new axon resulting in Fiber type grouping
  • Should that fiber become damaged and no healthy axons are there to re-innervate the result is Group atrophy
47
Q

What occurs as a result of segmental myocyte degeneration?

A
  • Release of creatine kinase
  • Results in phagocytosis and activation of satellite cells to regenerate
  • Continuity of original myofiber may be resorted or lead to deposition of collagen and fatty infiltrate
48
Q

What occurs during regeneration of myocytes?

A
  • cells are recruited from satellite precursor cells
  • they have large internalized nuclei and prominent nucleoli
  • basophilic cytoplasm due to increased synthesis and RNA content
49
Q

What are the signs/symptoms of dermatomyositis?

A
  • Eyelid rash most common
    • increased capillary loops
  • Scaling erythematous eruptions
    • Gottron’s papules at points of contact
  • Symetric weakness affecting proximal muscles first and distal later
  • Dysphagia
  • ILD, vasulitis, myocarditis
  • Juvenile form: calcinosis and GI involvment
50
Q

Dermatomyositis:

Where is inflammatory infiltrate found?

Type of muscle atrophy?

A
  • Infiltrate around small vessels and in perimysial CT
  • Muscle atrophy
    • perifascicular
    • hypoperfusion and fibrosis possible cause for perifascicular atrophy
      • small vessel damage is a key contributor
51
Q

Dermatomyositis:

3 autoantibodies involved and associations?

A
  • Anti-Mi2 helicase
    • involved in nucleosome remodeling
    • Gottren’s lesions
  • Anti-Jo1 to histidyl t-RNA synthetase
    • intersitial lung disease
  • Anti-P155/P140 to transcriptional regulators
    • perineoplastic
    • juvenile
52
Q

Polymyositis:

Onset?

Signs/symptoms?

A
  • Adult onset
    • no juvenile form like dermatomyositis
  • Proximal symmetric weakness
    • NO RASH
    • NO cutaneous involvement
53
Q

Polymyositis:

Gross and micro findings?

A
  • Direct injury to myofibers by CD8+ cell in endomysium
  • Necrotic and regenerative fibers present
  • No evidence of vascular injury
54
Q

Inclusion body myositis:

Onset?

Signs/symptoms?

A
  • Late adulthood: most common type 65+
  • Involvement of DISTAL muscles
55
Q

Inclusion body myositis:

Micro and EM findings?

A
  • Rimmed vacuoles
    • basophilic granules at the periphery
  • Vacuolated fibers stain with congo red
  • EM: tubular and filamentous inclusions
    • Beta amyloid
    • TDP-43
    • Ubiquitin
56
Q

What are the two drug induced toxic myopathies?

A
  • Statins: unrelated to dose or subtype
  • Chloroquine and Hydrochloroquine
    • proximal myopathy
    • lysosomal storage myopathy
    • vacuoles within myocytes
    • predominantely TI
57
Q

What is ICU myopathy?

Complications?

A
  • Weakness associated with treatment involving steroid treatment
  • May have selective loss of myosin (thick fil.)
  • Complication: problems weaning from ventilators
58
Q

4 Steroid mypathies? What do they cause?

A
  • Endogenous
    • cushings, adrenal tumors
  • Exogenous
    • treatment of asthma, COPD, RA
  • Acute - less common
    • rhabdomyolysis
  • Chronic
    • proximal limb weakness as well as neck flexors
    • recovery in weeks to months following reduction/discontinuation
59
Q

What occurs in thyrotoxic myopathy?

A
  • Acute or chronic proximal muscle weakness
  • Exophthalmic ophthalmoplegia
  • Myofiber damage with regeneration
  • Focal myofibril degeneration with fatty infiltrates
60
Q

Hypothyroid effects on muscle?

A
  • Cramps with slow reflexes and movements
  • Fiber atrophy and increased internal nuclei
  • Accumulation of glycogen aggregates or mucopolysaccharides
61
Q

Binge/Acute alcohol myopathy involves?

A
  • Rhabdomyolysis and myoglobinuria
    • dark urine and possible RF
  • Acute pain (general or local)
  • Swelling of myocytes, necrosis, myophagocytosis, and regeneration
  • Type I more suceptible
62
Q

Chronic alcoholic myopathy damage?

A
  • Type II fiber atrophy
  • Painless weakness
63
Q

DMD:

Genetics and gene product damage?

A
  • DMD gene on Xp21 - X-linked
  • Loss of Dystrophin
    • protein interface between intracellular contractile apparatus and the ECM
    • leads to weakness of the cell cytoskeleton
  • Due to deletions with a frameshift mutation most commonly
64
Q

Clinical manifestation of DMD?

A
  • Early motor milestones met on time but slowly develops clumsiness and mental retardation
  • Weakness begins in pelvic girdle muscles and extends to shoulder. Use of arms to get up =
    • GOWER’S SIGN
  • Enlargement of calf muscles: PSEUDOHYPERTROPHY
    • increase in the size of muscle fibers and later replacement by fat and CT
  • Death in 20s due to resp/cardiac complications
65
Q

DMD:

Gross and micro morphology?

A
  • Both TI and TII fibers as well as both small and large fibers involved
  • Increased internalized nuclei
  • Degeneration/necrosis/phagocytosis –> regeneration (basophilic cyto) –> proliferation of endomysial CT
    • this cycles and in later stages the muscle is replaced by fat and CT
66
Q

Becker MD:

Inheritance?

Symptoms and onset?

A
  • Also X-linked recessive but less common and less severe
  • Begins later: childhood or adolescnece
  • Involves changes but not loss of dystrophin
    • abnormal molecular weight
    • truncated (?) but still ahs some function
  • Nearly normal life span
67
Q

Myotonic dystrophy:

Inheritance pattern?

Pathogenesis?

A
  • Autosomal Dominant
  • CTG repeats in protein kinase gene DMPK
    • C19
    • normal - 30 repeats
    • Several thousand in severely affected
    • Trait demonstrates anticipation
68
Q

Myotonic dystrophy:

Micro and gross morphology?

A
  • Variable fiber size; mostly TI
  • Increased internal nuclei
  • Ring fibers
    • subsarcolemma band of cyto around myofibrils
  • Myofibrils oriented in CIRCULAR manner
  • Dystrophic muscle spindle fibers
    • splitting, necrosis, regeneration
    • ONLY dystrophy to involve spindles
69
Q

Myotonic dystrophy:

Clinical presentation?

A
  • Patients complain of stiffness
  • Late childhood gait difficulty
  • Progresses to hand/wrist weakness
  • Face muscle atrophy
    • ptosis
    • cataracts
  • Frontal balding
  • Gonadal atrophy
  • cardiomyopathy
  • abnormal glucose tolerance
  • dementia
  • sudden involuntary contractures
70
Q

Emery Dreifuss muscular dystrophy:

Clinical findings?

Pathological finding?

A
  • Clinical
    • slowly progressive onset
    • prominent contractures
  • Path
    • normal gene products localize to inner face of nuclear membrane
71
Q

Facioscapulohumeral muscular dystrophy:

Clinical?

Pathological findings?

A
  • Clinical
    • variable onset
    • weakness of face, neck, and shoulder
  • Path
    • dystrophic myopathy often with inflammatory infiltrate
72
Q

Congenital muscular dystrophy:

types? Clinical findings?

A
  • Congenital musuclar dystrophy
    • neonatal hypotonia
    • respiratory insuff
    • delayed milestones
  • With CNS malformation
    • neonatal hypotonia and MR
  • With CNS and ocular malformation
    • neonatal hypotonia and MR
    • cerebral and ocular malformations
73
Q

Type 1 Limb girdle dystrophies:

Inheritance?

3 types?

A

Autosomal dominant

  • Myotilin: facial sparing, dysrthric speech
  • Lamin A/C: arrhythmia and cardiomyopathy
  • Caveolin 3 - mild course
74
Q

Type 2 Limb girdle dystrophies:

Inheritance?

Main type?

A
  • Autosomal recessive
  • Sarcoglycan: severe course
    • duchenne like
75
Q

Limb Girdle muscular dystrophies:

Typical onset?

Clinical?

A
  • Onset as adolescents or young adults
  • Weakness proximal in upper and lower extremities
  • Variable findings and progression of dystrophic myopathy
76
Q

Central core disease:

Inheritance and genetics?

Clinical?

Pathologic?

A
  • AD Ryanodine receptor 1 mutation
  • Clinical:
    • Floppy infant
    • Early hypotonia, weakness, skeletal deformities
    • may develop malignant hyperthermia
  • Path:
    • cytoplasmic cores are lightly eosinophilic
    • decreased mitochondria
77
Q

Nemaline myopathy:

Several causes - mostly what inheritance?

Clinical variation?

Pathologic findings?

A
  • Autosomal recessive
  • Majority either childhood weakness or floppy infant with hypotonia
  • Path
    • aggregates of subsarcolemmal spindle shaped rods
      • nemoline rods
    • Primarily affect TI fibers
    • Rods are derived from Z-band material
      • alpha actinin
78
Q

Spinal muscular atrophy:

Also known as?

Inheritance?

Genetics?

A
  • Infantile motor neuron disease
  • AR
  • Mutations in Survival Motor Neuron gene 1
    • SMN1 on C5 (mostly deletions)
    • Contiguous region has variable # of homologous SMN2 gene
    • type of disease depends on variable copies of SMN2
79
Q

Spinal muscular atrophy:

3 types?

A
  • SMA1 - Werdnig Hoffman disease (severe)
    • floppy infant and death within 3 yrs
    • Severe loss of LMN
    • Profound neurogenic atrophy
  • SMA2
    • 3-35month presentation and survives more than 4 years
  • SMA3
    • presents after 2 years - adult lifespan
    • Least damage: so most SMN2
80
Q

What is the result of carnitine palmitoyltransferase II deficiency?

A
  • Lipid myopathy
    • Carnitine transport system abnormalities or mitochondrial dehydrogenase deficiency blocks FATTY ACID OXIDATION
  • Accumulation of lipid droplets in myocytes
    • vacuoles primarily type I
81
Q

Clinical presentation of lipid myopathies (aka carnitine palmitoyltransferase II deficiency)?

A
  • Muscle pain, tightness, myoglobinuria following prolonged exercise or exercise with fasting
    • rhabdomyolysis and RF possible
  • Cardiomyopathy and fatty liver may also occur
82
Q

Difference between McArdle disease and Pompe’s disease?

A
  • Both are glycogen storage diseases
  • McArdle
    • myophosphorylase deficiency
    • more common
    • episodic muscle damage with exercise
  • Pompes
    • Acid maltase deficiency
    • Lysosomal accumulation of glycogen
    • Severe - early presentation; mild - adult onset
83
Q

Mitochondrial myopathy:

Clinical?

A
  • Clinical: proximal weakness
    • sometimes severe involvement of extraocular muscles
    • neurological symptoms
    • lactic acidosis
    • cardiomyopathy
84
Q

Mitochondrial myopathy:

Gross/micro findings?

A
  • Aggregates of abnormal mitochondria
    • typically under sarcolemma
  • Ragged red fibers
    • distorted myofibrils that are irregular in outline
  • “Parking lot inclusions”
    • abnormal cristae with paracrystalline pattern
85
Q

Ion channel myopathies may have relapsing episodes of hypotonic paralysis:

What is this induced by?

Association with what channels?

A
  • Induced by exercise, cold, or high-carb meals
  • Associated with either hyper, hypo, or normaokalemia
    • Hyperkalemic hypotonia: SCM4A (Na channel)
    • Hypokalemic hypotonia: CACA1S voltage gated L-type calcium channel
86
Q

Malignant hyperthermia:

Triggered by? Result?

A
  • Triggered by anesthetics
    • halogenated hydrocarbons
    • succinylcholine
  • Results in tachycardia, tachypnea, muscle spasm, and hyperpyrexia
87
Q

Malignant hyperthermia:

Familial suceptibility with herditary muscle diseases affects withat receptor? Downstream effect?

Diagnosis?

A
  • Ryanodine receptor 1
    • mutant receptor allows uncontrolled efflux of Ca++ from sarcoplasm after exposure to anesthetic inducting contraction, tetany, increased muscle metabolism, and excessive heat production
  • Diagnosis by contraction response of biopsied muscle to anasthetic or identification of gene mutation

Pathology (11 decks)

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